Induction welding using a heat sink and/or cooling

ABSTRACT

A heat sink for use in induction welding includes a flexible backing and a number of tiles disposed on the flexible backing in a single layer, wherein the tiles are electrically non-conductive and thermally conductive.

INTRODUCTION

The present disclosure relates to induction welding. More specifically,the present disclosure relates to induction welding of thermoplasticcomposites using a flexible heat sink and/or cooling to reducetemperatures away from the weld interface.

BACKGROUND

Induction welding may be used to fuse or join thermoplastic composite(TPC) parts together. TPC parts generally include a thermoplastic whichare reinforced with non-plastic materials, such as carbon fibers. TPCparts offer high damage tolerance as well as moisture and chemicalresistance and do not degrade in hot or wet conditions. Moreover, TPCparts can be re-melted, providing benefits in repair and end-of-liferecyclability as well as reduced handling and storage costs whencompared to other alternatives.

Induction welding involves moving an induction coil along a weld line ofthe TPC parts. The induction coil induces eddy currents in theinherently conductive carbon fibers disposed within the TPC parts, whichgenerate heat and melt the thermoplastic with the intention toparticularly melt the thermoplastic at the weld interface. Compressionof the TPC parts together creates a fusion bond or weld joint. Inductionwelding produces a weld joint that is considered to be one solid piecesuch that two or more parts become one part.

While induction welding is effective, the induction coil generates heatthroughout the TPC parts and not just at the weld joint. For example,heating is higher in the portions of the TPC parts closer to theinduction coil than at the weld joint. Thus, there is a need in the artfor systems and method of induction welding TPC parts that concentrateheating at the weld joint.

SUMMARY

A heat sink for use in induction welding is provided. The heat sinkincludes a flexible backing and a number of tiles disposed on theflexible backing in a single layer, wherein the tiles are electricallynon-conductive and thermally conductive.

In another example, a method of induction welding a first carbon fiberthermoplastic composite (TPC) to a second carbon fiber thermoplasticcomposite (TPC) is provided. The method includes forming a weldinterface area between the first TPC and the second TPC, placing a heatsink onto a surface of the first TPC above the weld interface area,inductively heating the weld interface area, moving a gas through theheat sink, and dissipating heat absorbed by the heat sink bytransferring the heat from the heat sink to the gas.

In another example, a system for induction welding a first thermoplasticcomposite (TPC) to a second thermoplastic composite (TPC) at a weldinterface area is provided. The system includes a heat sink disposed onthe first TPC, the heat sink having a number of tiles flexibly joinedtogether by a backing and having an air gap disposed between the tiles,and an induction coil configured to inductively weld the first TPC tothe second TPC at the weld interface area, the induction coil disposedadjacent the heat sink.

The features, functions, and advantages that have been discussed may beachieved independently in various aspects or may be combined in otheraspects further details of which can be seen with reference to thefollowing description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a perspective view of a system for induction welding,according to an exemplary aspect;

FIG. 1A is a perspective view of a variation of the system for inductionwelding, according to an exemplary aspect;

FIG. 2 is an enlarged portion of a heat sink indicated by arrows 2-2 inFIG. 1, according to an exemplary aspect;

FIG. 2A is a perspective view of the heat sink shown on an exemplarycurved surface, according to an exemplary aspect;

FIG. 3 is a perspective view of a heat sink fabrication system used tofabricate the heat sink of FIG. 2, according to an exemplary aspect;

FIG. 4 is an exemplary process flow diagram illustrating a method offabricating the heat sink of FIG. 2 using the heat sink fabricationsystem of FIG. 3, according to an exemplary aspect;

FIG. 5 is an exemplary perspective view of a portion of a heat sinkhaving a mechanical hinge, according to an exemplary aspect;

FIG. 5A is a cross-section of the heat sink viewed in the direction ofarrow 5A-5A in FIG. 5, according to an exemplary aspect;

FIG. 6 is an enlarged, partial cross-section of a lay-up of the systemviewed in the direction of arrows 6-6 in FIG. 1, according to anexemplary aspect;

FIG. 7 is an exemplary process flow diagram illustrating a method ofinduction welding, according to an exemplary aspect;

FIG. 8 is an enlarged, partial cross-section of another lay-up of thesystem viewed in the direction of arrows 6-6 in FIG. 1, according to anexemplary aspect;

FIG. 9 is an enlarged, partial cross-section of another lay-up of thesystem viewed in the direction of arrows 6-6 in FIG. 1, according to anexemplary aspect;

FIG. 10 is an enlarged, partial cross-section of another lay-up of thesystem viewed in the direction of arrows 6-6 in FIG. 1, according to anexemplary aspect;

FIG. 11 is an enlarged, partial cross-section of another lay-up of thesystem viewed in the direction of arrows 6-6 in FIG. 1, according to anexemplary aspect;

FIG. 12 is an enlarged, partial cross-section of another lay-up of thesystem viewed in the direction of arrows 6-6 in FIG. 1, according to anexemplary aspect;

FIG. 13 is an exemplary process flow diagram of induction welding,according to an exemplary aspect;

FIG. 14 is another exemplary process flow diagram of induction welding,according to an exemplary aspect;

FIG. 15 is an enlarged, partial cross-section of another lay-up of thesystem viewed in the direction of arrows 6-6 in FIG. 1, according to anexemplary aspect;

FIG. 16 is an enlarged, partial cross-section of another lay-up of thesystem viewed in the direction of arrows 6-6 in FIG. 1, according to anexemplary aspect;

FIG. 17 is an exemplary process flow diagram of induction welding,according to an exemplary aspect;

FIG. 18 is another exemplary process flow diagram of induction welding,according to an exemplary aspect;

FIG. 19 is a perspective view of another example of a heat sink withliquid cooling, according to an exemplary aspect;

FIG. 20 is an exemplary process flow diagram illustrating a method offabricating the heat sink with liquid cooling of FIG. 19 using the heatsink fabrication system of FIG. 3, according to an exemplary aspect;

FIG. 21 is a perspective view of the heat sink fabrication system usedto fabricate the heat sink with liquid cooling of FIG. 19, according toan exemplary aspect;

FIG. 22 is an enlarged cross-section of another lay-up of the systemviewed in the direction of arrows 6-6 in FIG. 1 using the heat sink withliquid cooling, according to an exemplary aspect;

FIG. 23 is a perspective view of another example of a heat sink withliquid cooling, according to an exemplary aspect;

FIG. 24 is a perspective view of another example of a heat sink withliquid cooling, according to an exemplary aspect;

FIG. 25 is a top view of another example of a heat sink used duringinduction welding, according to an exemplary aspect;

FIG. 26 is a cross-section view of the heat sink viewed in the directionof arrows 26-26 in FIG. 25, according to an exemplary aspect;

FIG. 27 is a cross-section view of a variation of the heat sink shown inFIG. 25, according to an exemplary aspect;

FIG. 28 is a schematic view of a system for induction welding using theheat sink shown in FIG. 25, according to an exemplary aspect;

FIG. 29 is a schematic view of the system for induction welding usingthe heat sink shown in FIG. 25, according to another exemplary aspect;

FIG. 30 is a flow diagram of aircraft production and servicemethodology; and

FIG. 31 is a block diagram of an aircraft.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

Referring to FIG. 1, a schematic diagram of a system 10 for inductionwelding a first thermoplastic composite (TPC) 12 to a second TPC 14 isshown. The system 10 may be employed in the context of aircraftmanufacturing and service, as will be described below. For example, thesystem 10 may be used in component and subassembly manufacturing of anaircraft including interior fabrication, acoustic panels, systemintegration of the aircraft, airframe fabrication, and routinemaintenance and service of the aircraft. However, the system 10 may beused in various other industries, including automotive, construction,sporting goods, and general transportation industry, to name but a few.The first TPC 12 and the second TPC 14 are illustrated as flat sheets.However, it should be appreciated that the first TPC 12 and the secondTPC 14 may be contoured, curved, or otherwise non-planar, withoutdeparting from the scope of the present disclosure, as described inrelation to FIG. 2 below. Moreover, the first TPC 12 and the second TPC14 may be comprised of various thermoplastics reinforced with variouselectrically conductive materials. In one example, the thermoplasticsare selected from the group consisting of semi-crystallinethermoplastics and amorphous thermoplastics. The semi-crystallinethermoplastics may include polyphenylene sulfide (PPS),polyetheretherketone (PEEK), polyetherketoneketone (PEKK) andpolyarylketone (PAEK). The amorphous thermoplastics may includepolyetherimide (PEI). The semi-crystalline thermoplastic have highconsolidation temperatures with good mechanical properties relative toconventional thermoplastics. The amorphous thermoplastics exhibit agradual softening on heating with the material having good elongation,toughness and impact resistance properties relative to conventionalthermoplastics. Semi-crystalline thermoplastics contain areas of tightlyfolded chains (crystallites) that are connected together and exhibit asharp melting point on heating when the crystalline regions startdissolving. As the polymer approaches its melting point, the crystallinelattice breaks down and the molecules are free to rotate and translate.During slow cooling, the semi-crystalline thermoplastic nucleate andgrow crystalline regions which provides increased strength, stiffness,solvent resistance and temperature stability relative to an amorphousstructure. If a semi-crystalline thermoplastic is cooled too quickly itmay form an amorphous structure.

In another example, the electrically conductive materials include carbonfibers. The carbon fibers may be oriented within the thermoplastic invarious configurations (not shown), which in turn affects the degree ofheating during induction welding. For example, the carbon fibers may beoriented in a cross-hatch pattern at 0 and 90 degrees, +/−45 degrees, or+/−60 degrees, to name but a few. The carbon fibers may beunidirectional or weaved together. Each such configuration impacts thedegree of heating in the first TPC 12 and the second TPC 14 under agiven magnetic field. It should be appreciated that while two TPC partsare illustrated, any number of stacked TPC parts may be employed.

The system 10 generally includes a tooling base 16, an induction welder18, and a heat sink 20. The tooling base 16 supports the first TPC 12and the second TPC 14 thereon. In the example provided, the tooling base16 is flat. However, it should be appreciated that the tooling base 16may have various other shapes to support the first TPC 12 and the secondTPC 14.

The induction welder 18 is configured to inductively heat the first TPC12 and the second TPC 14 and may take various forms without departingfrom the scope of the present disclosure. In the example provided, theinduction welder 18 includes an induction coil 22 mounted to a roboticarm 24. The induction coil 22 may also be mounted to any other suitablerobotic manipulator. In another aspect, the induction coil 22 may befixed and the first TPC 12 and the second TPC 14 are moved relative tothe induction coil 22. Thus, the induction coil 22 may move relative tothe first TPC 12 and the second TPC 14 and the first TPC 12 and thesecond TPC 14 may be moved relative to the induction coil 22. In anotherexample, both the induction coil 22 and the first TPC 12 and the secondTPC 14 may move. The induction coil 22 generates a magnetic field 25 toinduce eddy currents in the carbon fibers of the first TPC 12 and thesecond TPC 14. The robotic arm 24 moves the induction coil 22 along aweld line 26 in a first direction 26A. Thus, the weld line 26 is an areaof the first TPC 12 and the second TPC 14 that is to be welded together.The weld line 26 may be straight or curved or any other pattern. A firstroller 28A and a second roller 28B are disposed adjacent the inductioncoil 22. The first roller 28A is disposed on a forward side 22A of theinduction coil 22. The second roller 28B is disposed on an aft side 22Bof the induction coil 22. The first roller 28A and the second roller 28Bapply consolidating pressure onto the first TPC 12 and the second TPC 14during the induction welding process, as will be described below. In theexample provided, the first roller 28A and the second roller 28B areconnected to the induction coil 22, though it should be appreciated thatthe first roller 28A and the second roller 28B may be separate withoutdeparting from the scope of the present disclosure. The first roller 28Aand the second roller 28B may be hinged to allow the first roller 28Aand the second roller 28B to move over contoured surfaces whilemaintaining consolidating pressure onto the first TPC 12. In addition,consolidating pressure may be applied during or after induction weldingwhen the induction coil 22 is moved in the first direction 26A or in anopposite direction. In addition, other methods may be employed to applythe consolidating pressure as described below with reference to FIG. 1A.

The induction welder 18 is in electrical communication with a controller30. The controller 30 is operable to control an amount of currentsupplied to the induction coil 22 which in turn controls the strength ofthe magnetic field and thus the heating of the first TPC 12 and thesecond TPC 14. The controller 30 is also operable to control movement ofthe robotic arm 24 or the induction coil 22 relative to the weld line26. The controller 30 is a non-generalized, electronic control devicehaving a preprogrammed digital computer or processor 32, memory ornon-transitory computer readable medium 34 used to store data such ascontrol logic, software applications, instructions, computer code, data,lookup tables, etc., and input/output ports 36. The non-transitorycomputer readable medium 34 includes any type of medium capable of beingaccessed by a computer, such as read only memory (ROM), random accessmemory (RAM), a hard disk drive, a compact disc (CD), a digital videodisc (DVD), or any other type of memory. A “non-transitory” computerreadable medium excludes wired, wireless, optical, or othercommunication links that transport transitory electrical or othersignals. A non-transitory computer readable medium includes media wheredata can be permanently stored and media where data can be stored andlater overwritten, such as a rewritable optical disc or an erasablememory device. Computer code includes any type of program code,including source code, object code, and executable code. The processor32 is configured to execute the code or instructions.

The system 10 may further include a number of sensors 38 in electroniccommunication with the controller 30. The sensors 38 are configured todetect or sense conditions of the first TPC 12 and/or the second TPC 14during the induction welding in order to provide real-time feedback tothe controller 30. For example, the sensors 38 may be infra-redtemperatures sensors configured to detect a temperature of the first TPC12 and/or the second TPC 14. Alternatively, or in addition, the sensors38 may be electromagnetic field sensors configured to detect a strengthof the magnetic field 25 generated by the induction coil 22. The sensors38 may be used by the controller 30 in feedback control of movement ofthe induction coil 22, as will be described below.

FIG. 1A shows an alternate arrangement of the system 10 according to theprinciples of the present disclosure. The arrangement shown in FIG. 1Ais similar to that shown in FIG. 1, however, the rollers 28A and 28Bhave been removed and the second TPC 14 is illustrated as having an “L”shaped cross-section. Other possible cross-sections for the second TPC14, and/or the first TPC 12, include at least “J”, “I”, “T”, “Z” and/or“Hat” cross-sections. Consolidating pressure is supplied by a bellows 39disposed along the weld line 26 below the second TPC 14. Expansion ofthe bellows 39 to exert a consolidating pressure onto the second TPC 14may be controlled by the controller 30.

Returning to FIG. 1, the heat sink 20 is configured to absorb anddissipate heat from the first TPC 12. The heat sink 20 is disposedbetween the first TPC 12 and the induction coil 22, as will be describedbelow. FIG. 2 shows an enlarged portion of the heat sink 20 of FIG. 1.Referring to FIG. 2, the heat sink 20 includes a number of tiles 40connected by a joint 42. The joint 42 is disposed between the tiles 40.The tiles 40 are made from an electrically non-conductive and thermallyconductive material. Thus, when under the induction coil 22 (FIG. 1),the tiles 40 are not heated by the magnetic field 25 but absorb heatfrom the first TPC 12. In one example, the tiles 40 have a thermaldiffusivity of greater than about 25 mm²/sec and preferably greater thanabout 70 mm²/sec. In this context, the term “about” is known to thoseskilled in the art. Alternatively, the term “about” may be read to meanplus or minus 5 mm²/sec. In another example, the tiles 40 have a thermalconductivity of greater than about 75 W/mK and preferably greater thanabout 150 W/mK. In this context, the term “about” is known to thoseskilled in the art. Alternatively, the term “about” may be read to meanplus or minus 10 W/mK. In another example, the tiles 40 have a specificheat capacity of greater than about 500 J/K/kg and preferably greaterthan about 700 J/K/kg. In this context, the term “about” is known tothose skilled in the art. Alternatively, the term “about” may be read tomean plus or minus 50 J/K/kg. In one example, the tiles 40 are comprisedof Aluminum Nitride. The Aluminum Nitride has a low residual carbon inthe material matrix to assure that during induction welding of the firstTPC 12 that the induction coil 22 does not couple with the carbon in thetiles 40 and inadvertently heat the tiles 40. In another example, thetiles 40 are comprised of Beryllium Oxide. In another example, the tiles40 are comprised of Cubic Boron Nitride (c-BN) or Hexagonal BoronNitride (h-BN).

The joint 42 flexibly holds the tiles 40 together and providesflexibility to the heat sink 20, thus allowing the heat sink 20 toconform to the contours of the first TPC 12. For example, FIG. 2Aillustrates the heat sink 20 on a contoured surface 43 of the first TPC12. In the example provided, the contoured surface 43 is curved. Theheat sink 20 pivots at the joints 42 to maintain contact between thetiles 40 and the contoured surface 43. The joint 42 may be comprised ofeither a flexible adhesive 45, shown in FIGS. 2 and 2A, or a mechanicalhinge 47, shown in FIG. 5. With reference to FIG. 2, the flexibleadhesive 45 provides flexibility to the heat sink 20 and does not meltduring heating of the tiles 40 during induction welding. A minimumamount of flexible adhesive 45 is preferably used to hold the tiles 40together, thus increasing the heat dissipation capacity of the heat sink20. Accordingly, in one example, the flexible adhesive 45 has along-term degradation temperature greater than about 570 degreesFahrenheit in air. In this context, the term “about” is known to thoseskilled in the art. Alternatively, the term “about” may be read to meanplus or minus 25 degrees Fahrenheit. In another example, the flexibleadhesive 45 has an elongation of between 120% and 670%. In anotherexample, the flexible adhesive 45 has a tensile strength of between 690psi to 1035 psi. In another example, the flexible adhesive 45 has a tearstrength (Die B) of between 31 lb/in to 190 lb/in. Accordingly, in oneexample, the flexible adhesive 45 is comprised of a silicone. An exampleof a suitable silicone is 3145 RTV by Dow Corning. However, othersilicones may be employed.

The tiles 40 are arranged in a single layer as a parquet or geometricpattern. Thus, each of the tiles 40 define a gap 44 therebetween and thejoint 42 is disposed within the gap 44. The tiles 40 are arranged, sizedand shaped to help facilitate conformance to a contour of the contouredsurface 43 (FIG. 2A) of the first TPC 12. In one example, the gap 44 hasa width 49 between about 0.005 inches to about 0.1 inches and preferablyabout 0.040 inches. In this context, the term “about” is known to thoseskilled in the art. Alternatively, the term “about” may be read to meanplus or minus 0.005 inches. While the tiles 40 are illustrated assquares, which maximize a surface area of the tiles 40 relative to thejoint 42, the tiles 40 may have various other shapes without departingfrom the scope of the present disclosure. For example, the tiles 40 mayhave straight or curved edges and have three or more sides to helpconform to a contour of the first TPC 12 and/or the shape of the weld.The heat sink 20 is sized to preferably at least cover the weld line 26(FIG. 1) or, as in the present example, the entire first TPC 12 (FIG.1).

FIG. 3 shows a heat sink fabrication system 50 used to fabricate theheat sink 20 (FIG. 2). The heat sink fabrication system 50 includes abase plate 52 that supports an backing material 54. In one example, thebacking material 54 is a double-sided tape that adheres to the baseplate 52. In another example, the backing material 54 is a glass clothtape. In yet another example, the backing material 54 is a Teflon coatedfiberglass sprayed with an adhesive having a bottom layer of glasscloth. In this configuration, curing occurs on both sides of the backingmaterial 54. A frame 56 having a jig 58 is disposed on the backingmaterial 54. In one aspect, the jig 58 is comprised of individual wires59 weaved together. The jig 58 is sized to create the gaps 44 (FIG. 2)in the heat sink 20. The frame 56 and the jig 58 is removable from thebacking material 54.

FIG. 4 shows a flow chart of a method 60 for creating the heat sink 20of FIG. 2 using the heat sink fabrication system 50 of FIG. 3. Themethod 60 begins at block 60A where the tiles 40 may be primed by aprimer prior to arrangement onto the backing material 54. In oneexample, the primer is a silicone primer. At block 60B the tiles 40 arearranged into a pattern within the jig 58. For example, the tiles 40 areplaced onto the backing material 54 between the jig 58. The backingmaterial 54 holds the tiles 40 in place while the jig 58 spaces thetiles 40. Thus, the pattern is defined by the jig 58. At block 60B Oncethe tiles 40 have been placed, the frame 56 and the jig 58 are removedat block 60C thus leaving the gaps 44 between the tiles 40.

Next, at block 60D, the tiles 40 are flexibly joined together with thejoint 42. In the example provided, the joint 42 is applied within thegaps 44 between the tiles 40. At block 60E the joint 42 is thenpreferably cured over a period of time. Once cured, the assembled heatsink 20 may be removed from the backing material 54 at block 60F.

FIG. 5 shows a portion of the heat sink 20 employing an example of themechanical hinge 47 flexibly connecting the tiles 40. A first tile 40Aincludes tabs 65 that extend out from a number of sides 66 of the firsttile 40A. The tabs 65 may be integrally formed with the first tile 40Aor bonded to the first tile 40A. An adjacent, second tile 40B includesslots 67 disposed in a number of sides 68 of the second tile 40B. Itshould be appreciated that, as described above, the first tile 40A andthe second tile 40B may have three or more sides without departing fromthe scope of the present disclosure. With reference to FIG. 5A, thefirst tile 40A is connected to the second tile 40B by inserting the tab65 within the slot 67. The tab 65 and the slot 67 are configured toallow the first tile 40A to pivot with respect to the second tile 40B.For example, the first tile 40A may pivot with respect to the secondtile 40B by +/−0 degrees. In one example, the flexible adhesive 45 (FIG.2) may be disposed within the mechanical hinge 47. The tiles 40A, 40Bare arranged in a single layer to form a parquet pattern. The heat sink20 may thus be fabricated to any size or shape by alternativelyconnecting a number of first tiles 40A to a number of second tiles 40B.

Returning to FIG. 1, the system 10 may further include a vacuum bag 70.The vacuum bag 70 is connected to a vacuum source 72. The vacuum source72 is configured to apply a vacuum to the vacuum bag 70. The vacuumsource 72 is preferably controlled by the controller 30. The first TPC12, the second TPC 14, and the heat sink 20 are all disposed within thevacuum bag 70. By removing air from the vacuum bag 70, the flexibleadhesive 45 of the joint 42 (FIG. 2) of the heat sink 20 is able towithstand temperatures before degrading higher than in an environmentwith air/oxygen. Alternatively, the vacuum source 72 may be replacedwith a pump (not shown) that fills the vacuum bag 70 with an inert gas,such as Nitrogen. The inert gas displaces the air within the vacuum bag70 and also allows the flexible adhesive 45 of the joint 42 (FIG. 2) ofthe heat sink 20 to withstand temperatures before degrading higher thanan environment with air/oxygen. The vacuum bag 70 is also configured toapply consolidating pressure onto the first TPC 12 and the second TPC 14via vacuum compression.

FIG. 6 shows a cross-section of a lay-up illustrating the first TPC 12,the second TPC 14, the heat sink 20, and the vacuum bag 70 on thetooling base 16 with a side view of the induction coil 22. The first TPC12 is disposed on top of the second TPC 14. A weld interface area 74 isdefined along the weld line 26 (FIG. 1) between the first TPC 12 and thesecond TPC 14. The heat sink 20 is disposed on top of the first TPC 12between the induction coil 22 and the first TPC 12. The induction coil22 is a distance “d” from the first TPC 12. In one example, the distanced is about 8 mm. The heat sink 20 has a thickness “t” that is less thanthe distance d. In one example, the thickness t is about 4 mm. In yetanother example, the heat sink 20 is cooled prior to being placed on thefirst TPC 12. The first roller 28A and the second roller 28B apply aconsolidating pressure on the first TPC 12 through the vacuum bag 70 andthe heat sink 20 to compress the first TPC 12 onto the second TPC 14. Inone example, the first roller 28A and the second roller 28B maintain theinduction coil 22 at a consistent height above the first TPC 12.

During induction welding, the controller 30 (FIG. 1) commands a currentthrough the induction coil 22 to generate the magnetic field 25. Themagnetic field 25 heats the carbon fibers within the first TPC 12 andthe second TPC 14. A portion 76 of the first TPC 12 closer to theinduction coil 22 is heated to a greater extent than at the weldinterface area 74. However, the heat sink 20 absorbs and dissipates theheat within the portion 76 of the first TPC 12. Thus, the heat generatedby the induction welder 18 is concentrated at the weld interface area74. When the thermoplastic at the weld interface area 74 is heated abovethe melting point, or consolidation temperature, of the material, thefirst roller 28A and the second roller 28B exert a consolidatingpressure on the first TPC 12 to merge the first TPC 12 with the secondTPC 14 at the weld interface area 74, thus creating a uniform fusionbond upon cooling. In one example, the weld interface area 74 is heatedapproximately 20 degrees above the consolidation temperature. Thecontroller 30 then commands the robotic arm 24 to move in the firstdirection 26A (FIG. 1) along the weld line 26 (FIG. 1) to weld the firstTPC 12 part to the second TPC 14. Feedback from the sensors 38 (FIG. 1)may be used to command different currents to the induction coil 22, thusadjusting the amount of heating in real time. The heat sink 20 alsoallows the first TPC 12 to cool at a rate to facilitate crystallizationof the semi-crystallinity thermoplastic in the weld interface area 74after induction welding, thus increasing the amount of crystallizationof the semi-crystallinity thermoplastic. For example, during inductionwelding the heat sink 20 absorbs heat in the tiles 40. After inductionwelding, the absorbed heat in the tiles 40 that is not dissipated intothe atmosphere is absorbed back into the first TPC 12, thus allowing thefirst TPC 12 to cool at a particular rate that increases the amount ofcrystallization. For example, an optimum cooling rate for PEEK is in therage of 0.2-20° F./min, which will yield a crystalline content of25-35%. The rate of crystallization is also dependent on the specificannealing temperature with the peak rate at about the mid-point betweenthe glass transition temperature (T_(g)) and the melting temperature(T_(m)).

With reference to FIG. 7, and continued reference to FIGS. 1 and 6, aflow chart of a method 80 for induction welding the first TPC 12 to thesecond TPC 14 using the system 10 is illustrated. The method 80 beginsat block 81 by aligning the first TPC 12 with the second TPC 14 to formthe weld interface area 74. Next, at block 82, the heat sink 20 isplaced on to the first TPC 12. As noted above, the heat sink 20preferably at least covers the weld interface area 74 along the weldline 26. Because the heat sink 20 is flexible, the heat sink 20 conformsto the surface contour of the first TPC 12, whether planar ornon-planar, as illustrated in FIG. 2A. In the example provided, thefirst TPC 12, the second TPC 14, and the heat sink 20 are all placedwithin the vacuum bag 70. A vacuum may then be applied to the vacuum bag70 by the vacuum source 72. The vacuum bag 70 applies a consolidatingforce of up to 1 atmosphere on the first TPC 12 and the second TPC 14.Alternatively, an inert gas may be pumped into the vacuum bag 70.

At block 83 the weld interface area 74 is inductively heated by theinduction coil 22. At block 84, heat generated in the portion 76 closestto the induction coil 22 is absorbed and dissipated by the heat sink 20thus cooling the portion 76. At block 85, the first roller 28A and thesecond roller 28B exert a consolidation pressure onto the first TPC 12to merge the first TPC 12 with the second TPC 14 at the weld interfacearea 74, thus creating a uniform fusion bond upon cooling. It should beappreciated that blocks 83, 84, and 85 may occur simultaneously. Inanother example, the bellows 39 (FIG. 1A) or other means may exert aconsolidating pressure onto the second TPC 14. At block 86, the weldinterface area 74 is inductively welded along the weld line 26 by movingthe induction coil 22 along the weld line 26 to weld the first TPC 12part to the second TPC 14. Alternatively, the weld interface area 74 maybe moved relative to the induction coil 22. At block 87, feedback fromthe sensors 38 is used to adjust the induction welding process in realtime. For example, the controller 30 may command different currents tothe induction coil 22, thus adjusting the amount of heating in realtime, command a speed between the induction coil 22 and the weldinterface area 74, etc.

FIG. 8 shows a cross-section of a lay-up of the first TPC 12, the secondTPC 14, the heat sink 20, and the vacuum bag 70 on the tooling base 16with a side view of the induction coil 22. However, a second heat sink78 is included. The second heat sink 78 is substantially similar to theheat sink 20.

The first TPC 12 is disposed on top of the second TPC 14. The heat sink20 is disposed on top of the first TPC 12 between the induction coil 22and the first TPC 12. The second heat sink 78 is disposed between thetooling base 16 and the second TPC 14. In addition, the second heat sink78 is disposed within the vacuum bag 70. During induction welding, asdescribed above, it is desirable to concentrate heat at the weldinterface area 74 and minimize heat in other areas of the first TPC 12and the second TPC 14. However, during induction welding, heat isgenerated in the first TPC 12, the weld interface area 74, and thesecond TPC 14. The heat sink 20 absorbs and dissipates heat generated inportion 76 of the first TPC 12. The second heat sink 78 absorbs anddissipates heat generated in a portion 88 of the second TPC 14 adjacentthe second heat sink 78. Thus, heat is concentrated along the weldinterface area 74 and not in the portion 76 of the first TPC 12 and notin the portion 88 of the second TPC 14.

FIG. 9 shows an enlarged cross-section of the system 10 illustratinganother example of a lay-up of the first TPC 12, the second TPC 14, theheat sink 20, and the vacuum bag 70 on the tooling base 16. However, thetooling base 16 includes a cooler unit 89 embedded therein.Alternatively, the cooler unit 89 may be disposed on a surface of thetooling base 16 (not shown). The cooler unit 89 is connected to acoolant source 90. The cooler unit 89 may include tubing within thetooling base 16 and the coolant source 90 may include a fluid heatexchanger and pump (not shown). The coolant source 90 is in electricalcommunication with the controller 30 (FIG. 1).

The first TPC 12 is disposed on top of the second TPC 14. The heat sink20 is disposed on top of the first TPC 12 between the induction coil 22and the first TPC 12. The second TPC 14 is disposed adjacent the coolerunit 89 within the tooling base 16. During induction welding, asdescribed above, it is desirable to concentrate heat at the weldinterface area 74. The cooler unit 89 acts as a heat exchanger for theportion 88 of the second TPC 14 adjacent the cooler unit 89 and reducesthe heat in the second TPC 14 while the heat sink 20 absorbs anddissipates heat in the first TPC 12. Thus, heat is concentrated alongthe weld interface area 74 and not in the portion 76 of the first TPC 12and the portion 88 of the second TPC 14.

FIG. 10 shows a cross-section of a lay-up of the first TPC 12, thesecond TPC 14, the heat sink 20, and the second heat sink 78 on thetooling base 16 with a side view of the induction coil 22. However, thevacuum bag 70 is replaced with a first plate 91 and a second plate 92.

The first TPC 12 is disposed on top of the second TPC 14. The heat sink20 is disposed on top of the first TPC 12 between the induction coil 22and the first TPC 12. The second heat sink 78 is adjacent the second TPC14. The first TPC 12, the second TPC 14, the heat sink 20, and thesecond heat sink 78 are all sandwiched between the first plate 91 andthe second plate 92. The first plate 91 and the second plate 92 providestability to the lay-up by preventing the first TPC 12, the second TPC14, the heat sink 20, and the second heat sink 78 from moving relativeto one another. The first roller 28A and the second roller 28B contactthe first plate 91 and provide consolidating pressure during inductionwelding, as described above.

FIG. 11 shows an enlarged, partial cross-section of the system 10illustrating another example of a lay-up of the first TPC 12, the secondTPC 14, and the vacuum bag 70 on the tooling base 16 using no heatsinks. However, the induction welder 18 includes a cooling apparatus 93.The cooling apparatus 93 is disposed adjacent the induction coil 22 inthe first direction 26A (FIG. 1). The cooling apparatus 93 is connectedto the induction coil 22 by a member 94 in order to fix a distancebetween the induction coil 22 and the cooling apparatus 93. However, itshould be appreciated that the cooling apparatus 93 may be separatewithout departing from the scope of the present disclosure. The coolingapparatus 93 includes a number of nozzles 96 configured to emit acoolant. The cooling apparatus 93 is connected to a coolant source 98 aswell as the controller 30. In one example, the coolant used is CO₂ gas.However, other coolants may be employed. As noted above, no heat sinksare employed in this example.

During induction welding, the cooling apparatus 93 cools the first TPC12 ahead of the induction coil 22 by emitting the coolant onto the firstTPC 12. In one example, the cooling apparatus 93 is configured to coolthe first TPC 12 to about −100 degrees Fahrenheit. In this context, theterm “about” is known to those skilled in the art. Alternatively, theterm “about” may be read to mean plus or minus 25 degrees Fahrenheit.Cooling the first TPC 12 creates a thermal gradient and keeps thetemperature of portion 76 of the first TPC 12 below the consolidationtemperature during induction welding. The thermal gradient is thetemperature difference at from the portion 76 of the first TPC 12adjacent the induction coil 22 relative to the temperature at the weldinterface area 74. The thermal gradient may be controlled by the numberof nozzles 96, a coolant flow rate from the nozzles 96, a distance fromcooling apparatus 93 to the induction coil 22, and the strength of themagnetic field generated by the induction coil 22, as well asthicknesses of the first TPC 12 and second TPC 14 and carbon fiberorientation. In addition, the amount of cooling and heating can beadjusted by the controller 30 in real-time based on feedback receivedfrom the sensors 38 (FIG. 1).

FIG. 12 shows a cross-section of a lay-up of the first TPC 12, thesecond TPC 14, the vacuum bag 70 on the tooling base 16 using no heatsinks with a side view of the induction coil 22. However, the inductionwelder 18 includes a second cooling apparatus 100 and a second inductioncoil 102. The second cooling apparatus 100 and the second induction coil102 are both disposed adjacent the induction coil 22 in a directionopposite the first direction 26A (FIG. 1). Thus, the second coolingapparatus 100 and the second induction coil 102 are disposed oppositethe cooling apparatus 93. The second cooling apparatus 100 and thesecond induction coil 102 are connected to the induction coil 22 by amember 104 in order to fix a distance between the induction coil 22 andthe second cooling apparatus 100 and the second induction coil 102.However, it should be appreciated that the second cooling apparatus 100and/or the second induction coil 102 may be separate without departingfrom the scope of the present disclosure. The second cooling apparatus100 includes a number of nozzles 106 configured to emit the coolant. Thesecond cooling apparatus 100 is connected to the coolant source 98 aswell as the controller 30. The second induction coil 102 is similar tothe induction coil 22 and is controlled by the controller 30. As notedabove, no heat sinks are employed in this example.

During induction welding, the cooling apparatus 93 cools the first TPC12 ahead of the induction coil 22 by emitting the coolant onto the firstTPC 12, as described above. As the induction welder 18 moves along theweld line 26 (FIG. 1), the induction coil 22 melts the weld interfacearea 74 and the first TPC 12 merges with the second TPC 14 under theconsolidating pressure from the first roller 28A and the second roller28B. In order to control a cooling of the weld interface area 74, thecontroller 30 heats and cools the merged weld interface area 74 usingthe second cooling apparatus 100 and the second induction coil 102. Therate of cooling at the weld interface area 74 is controlled bycontrolling the amount of cooling and heating by the controller 30 inreal-time based on feedback received from the sensors 38 (FIG. 1). Therate of cooling can be controlled to maximize crystallization of thethermoplastic at the weld interface area 74, thus increasing strength.

With reference to FIG. 13, and continued reference to FIGS. 1 and 11, aflow chart of a method 110 for induction welding the first TPC 12 to thesecond TPC 14 using the system 10 with the cooling apparatus 93 isshown. The method 110 begins at block 112 by aligning the first TPC 12with the second TPC 14 to form the weld interface area 74. In theexample provided, the first TPC 12 and the second TPC 14 are all placedwithin the vacuum bag 70. A vacuum may then be applied to the vacuum bag70 by the vacuum source 72. Alternatively, an inert gas may be pumpedinto the vacuum bag 70.

Next, at block 114, the first TPC 12 is cooled using the coolingapparatus 93. In one example, a target temperature at the weld interfacearea 74 or at the portion 76 is set by the controller 30. The controller30 then monitors an actual temperature of the weld interface area 74 orat the portion 76 during cooling by the cooling apparatus 93 using thesensors 38. The controller 30 then controls the amount of coolingprovided by the cooling apparatus 93 to match the actual temperaturewith the target temperature. The target temperature may be set using alook-up table or calculated given particular factors in order to achievea particular thermal gradient. For example, setting the targettemperature may determine a location of the weld interface area 74relative to the induction coil 22 and setting the target temperaturebased on the location of the weld interface area 74. Other factors mayinclude the number of nozzles 96, a coolant flow rate from the nozzles96, a distance from cooling apparatus 93 to the induction coil 22, andthe strength of the magnetic field generated by the induction coil 22,as well as thicknesses of the first TPC 12 and second TPC 14 and carbonfiber orientation, and a speed at which the induction coil 22 movesrelative to the weld interface area 74 or the speed at which the weldinterface area 74 moves relative to the induction coil 22, or both. Inanother example, the target temperature is set to about −100 degreesFahrenheit. In this context, the term “about” is known to those skilledin the art. Alternatively, the term “about” may be read to mean plus orminus 25 degrees Fahrenheit.

At block 116 the weld interface area 74 is inductively heated by theinduction coil 22. The thermal gradient created by first cooling thefirst TPC 12 keeps the temperature of the portion 76 closest to theinduction coil 22 below the consolidation temperature while allowing thetemperature of the weld interface area 74 to exceed the consolidationtemperature.

At block 118, the first roller 28A and the second roller 28B exert aconsolidation pressure onto the first TPC 12 to merge the first TPC 12with the second TPC 14 at the weld interface area 74, thus creating auniform fusion bond upon cooling. In another example, the bellows 39(FIG. 1A) or other means may exert a consolidating pressure onto thesecond TPC 14. At block 120, the weld interface area 74 is inductivelywelded along the weld line 26 by moving the induction coil 22 along theweld line 26 to weld the first TPC 12 part to the second TPC 14.Alternatively, the weld interface area 74 may be moved relative to theinduction coil 22. It should be appreciated that blocks 116, 118, and120 may occur simultaneously. At block 122, feedback from the sensors 38is used to adjust the induction welding process in real time. Forexample, the controller 30 may command different currents to theinduction coil 22, thus adjusting the amount of heating in real time,command a speed between the induction coil 22 and the weld interfacearea 74, etc.

With reference to FIG. 14, and continued reference to FIGS. 1 and 12, aflow chart of a method 130 for induction welding the first TPC 12 to thesecond TPC 14 using the system 10 with the cooling apparatus 93, thesecond cooling apparatus 100, and the second induction coil 102 isshown. The method 130 begins at block 132 by aligning the first TPC 12with the second TPC 14 to form the weld interface area 74. In theexample provided, the first TPC 12 and the second TPC 14 are all placedwithin the vacuum bag 70. A vacuum may then be applied to the vacuum bag70 by the vacuum source 72. Alternatively, an inert gas may be pumpedinto the vacuum bag 70.

Next, at block 134, the first TPC 12 is cooled using the coolingapparatus 93. In one example, a target temperature for the first TPC 12at the weld interface area 74 or the portion 76 is set by the controller30. The controller 30 then monitors an actual temperature of the firstTPC 12 at the weld interface area 74 or the portion 76 during cooling bythe cooling apparatus 93 using the sensors 38. The controller 30 thencontrols the amount of cooling provided by the cooling apparatus 93 tomatch the actual temperature with the target temperature. The targettemperature may be set using a look-up table or calculated givenparticular factors in order to achieve a particular thermal gradient.For example, setting the target temperature may determining a locationof the weld interface area 74 relative to the induction coil 22 andsetting the target temperature based on the location of the weldinterface area 74. Other factors may include the number of nozzles 96, acoolant flow rate from the nozzles 96, a distance from cooling apparatus93 to the induction coil 22, and the strength of the magnetic fieldgenerated by the induction coil 22, as well as thicknesses of the firstTPC 12 and second TPC 14 and carbon fiber orientation and speed of theinduction coil 22 relative to the weld interface area 74. In anotherexample, the target temperature is set to about −100 degrees Fahrenheit.In this context, the term “about” is known to those skilled in the art.Alternatively, the term “about” may be read to mean plus or minus 25degrees Fahrenheit.

At block 136 the weld interface area 74 is inductively heated by theinduction coil 22. The thermal gradient created by first cooling thefirst TPC 12 keeps the temperature of the portion 76 closest to theinduction coil 22 below the consolidation temperature while allowing thetemperature of the weld interface area 74 to exceed the consolidationtemperature.

At block 138, the first roller 28A and the second roller 28B exert aconsolidation pressure onto the first TPC 12 to merge the first TPC 12with the second TPC 14 at the weld interface area 74, thus creating auniform fusion bond upon cooling. In another example, the bellows 39(FIG. 1A) or other means may exert a consolidating pressure onto thesecond TPC 14. At block 140, the weld interface area 74 is inductivelywelded along the weld line 26 by moving the induction coil 22 along theweld line 26 to weld the first TPC 12 part to the second TPC 14.Alternatively, the weld interface area 74 may be moved relative to theinduction coil 22. It should be appreciated that blocks 136, 138, and140 may occur simultaneously. At block 142, feedback from the sensors 38is used to adjust the induction welding process in real time. Forexample, the controller 30 may command different currents to theinduction coil 22, thus adjusting the amount of heating in real time,command a speed between the induction coil 22 and the weld interfacearea 74, etc. At block 144 the second cooling apparatus 100 and/or thesecond induction coil 102 is used to control a rate of cooling of theweld interface area 74. The rate of cooling at the weld interface area74 is controlled by controlling the amount of cooling and heating by thecontroller 30 in real-time based on feedback received from the sensors38 (FIG. 1).

FIG. 15 shows a cross-section of a lay-up of the first TPC 12, thesecond TPC 14, and the vacuum bag 70 on the tooling base 16 using theheat sink 20 with a side view of the induction coil 22 and the coolingapparatus 93. In this example, the cooling apparatus 93 cools the heatsink 20 instead of directly cooling the first TPC 12. Cooling the heatsink 20 increases the thermal gradient and allows the heat sink 20 toremove more heat from the first TPC 12 during induction welding thanwithout cooling. In another example (not shown), the second heat sink 78may be used in addition to the heat sink 20.

FIG. 16 shows a cross-section of a lay-up of the first TPC 12, thesecond TPC 14, and the vacuum bag 70 on the tooling base 16 using theheat sink 20 with a side view of the cooling apparatus 93, the secondcooling apparatus 100, and the second induction coil 102. In thisexample, the second cooling apparatus 100 cools the heat sink 20 insteadof the directly cooling the first TPC 12 after induction welding by theinduction coil 22. The second induction coil 102 operates as previouslydescribed as the heat sink 20 is not electrically conductive. In anotherexample (not shown), the second heat sink 78 may be used in addition tothe heat sink 20.

With reference to FIG. 17, and continued reference to FIGS. 1 and 15, aflow chart of a method 150 for induction welding the first TPC 12 to thesecond TPC 14 using the system 10 with the cooling apparatus 93 and theheat sink 20 is shown. The method 150 begins at block 152 by aligningthe first TPC 12 with the second TPC 14 to form the weld interface area74.

Next, at block 154 the heat sink 20 is placed on to the first TPC 12. Asnoted above, the heat sink 20 preferably at least covers the weldinterface area 74 along the weld line 26. Because the heat sink 20 isflexible, the heat sink 20 conforms to the surface contour of the firstTPC 12, whether planar or non-planar, as illustrated in FIG. 2A. In theexample provided, the first TPC 12, the second TPC 14, and the heat sink20 are all placed within the vacuum bag 70. A vacuum may then be appliedto the vacuum bag 70 by the vacuum source 72. Alternatively, an inertgas may be pumped into the vacuum bag 70.

At block 156, the heat sink 20 is cooled using the cooling apparatus 93.In one example, a target temperature for the heat sink 20 is set by thecontroller 30. The controller 30 then monitors an actual temperature ofthe heat sink 20 during cooling by the cooling apparatus 93 using thesensors 38. The controller 30 then controls the amount of coolingprovided by the cooling apparatus 93 to match the actual temperaturewith the target temperature. The target temperature may be set using alook-up table or calculated given particular factors in order to achievea particular thermal gradient. For example, setting the targettemperature may determining a location of the weld interface area 74relative to the induction coil 22 and setting the target temperaturebased on the location of the weld interface area 74. Other factors mayinclude the number of nozzles 96, a coolant flow rate from the nozzles96, a distance from cooling apparatus 93 to the induction coil 22, andthe strength of the magnetic field generated by the induction coil 22,as well as thicknesses of the first TPC 12 and second TPC 14 and carbonfiber orientation. In another example, the target temperature is set toabout −100 degrees Fahrenheit. In this context, the term “about” isknown to those skilled in the art. Alternatively, the term “about” maybe read to mean plus or minus 25 degrees Fahrenheit.

At block 158 the weld interface area 74 is inductively heated by theinduction coil 22. The heat sink 20, cooled at block 156, keeps thetemperature of the portion 76 closest to the induction coil 22 below theconsolidation temperature while allowing the temperature of the weldinterface area 74 to exceed the consolidation temperature.

At block 160, the first roller 28A and the second roller 28B exert aconsolidation pressure onto the first TPC 12 to merge the first TPC 12with the second TPC 14 at the weld interface area 74, thus creating auniform fusion bond upon cooling. In another example, the bellows 39(FIG. 1A) or other means may exert a consolidating pressure onto thesecond TPC 14. At block 162, the weld interface area 74 is inductivelywelded along the weld line 26 by moving the induction coil 22 along theweld line 26 to weld the first TPC 12 part to the second TPC 14.Alternatively, the weld interface area 74 may be moved relative to theinduction coil 22. It should be appreciated that blocks 158, 160, and162 may occur simultaneously. At block 164, feedback from the sensors 38is used to adjust the induction welding process in real time. Forexample, the controller 30 may command different currents to theinduction coil 22, thus adjusting the amount of heating in real time,command a speed between the induction coil 22 and the weld interfacearea 74, etc. With reference to FIG. 18, and continued reference toFIGS. 1 and 16, a flow chart of a method 170 for induction welding thefirst TPC 12 to the second TPC 14 using the system 10 with the heat sink20, the cooling apparatus 93, the second cooling apparatus 100, and thesecond induction coil 102 is shown. The method 170 begins at block 172by aligning the first TPC 12 with the second TPC 14 to form the weldinterface area 74.

Next, at block 174 the heat sink 20 is placed on to the first TPC 12. Asnoted above, the heat sink 20 preferably at least covers the weldinterface area 74 along the weld line 26. Because the heat sink 20 isflexible, the heat sink 20 conforms to the surface contour of the firstTPC 12, whether planar or non-planar, as illustrated in FIG. 2A. In theexample provided, the first TPC 12, the second TPC 14, and the heat sink20 are all placed within the vacuum bag 70. A vacuum may then be appliedto the vacuum bag 70 by the vacuum source 72. Alternatively, an inertgas may be pumped into the vacuum bag 70.

At block 176, the heat sink 20 is cooled using the cooling apparatus 93.In one example, a target temperature for the heat sink 20 is set by thecontroller 30. The controller 30 then monitors an actual temperature ofthe heat sink 20 during cooling by the cooling apparatus 93 using thesensors 38. The controller 30 then controls the amount of coolingprovided by the cooling apparatus 93 to match the actual temperaturewith the target temperature. The target temperature may be set using alook-up table or calculated given particular factors in order to achievea particular thermal gradient. For example, setting the targettemperature may determining a location of the weld interface area 74relative to the induction coil 22 and setting the target temperaturebased on the location of the weld interface area 74. Other factors mayinclude the number of nozzles 96, a coolant flow rate from the nozzles96, a distance from cooling apparatus 93 to the induction coil 22, andthe strength of the magnetic field generated by the induction coil 22,as well as thicknesses of the first TPC 12 and second TPC 14, carbonfiber orientation, and speed of movement of the induction coil 22relative to the weld interface area 74. In another example, the targettemperature is set to about −100 degrees Fahrenheit. In this context,the term “about” is known to those skilled in the art. Alternatively,the term “about” may be read to mean plus or minus 25 degreesFahrenheit.

At block 178 the weld interface area 74 is inductively heated by theinduction coil 22. The heat sink 20, cooled at block 176, keeps thetemperature of the portion 76 closest to the induction coil 22 below theconsolidation temperature while allowing the temperature of the weldinterface area 74 to exceed the consolidation temperature.

At block 179, the first roller 28A and the second roller 28B exert aconsolidation pressure onto the first TPC 12 to merge the first TPC 12with the second TPC 14 at the weld interface area 74, thus creating auniform fusion bond upon cooling. In another example, the bellows 39(FIG. 1A) or other means may exert a consolidating pressure onto thesecond TPC 14. At block 180, the weld interface area 74 is inductivelywelded along the weld line 26 by moving the induction coil 22 along theweld line 26 to weld the first TPC 12 part to the second TPC 14.Alternatively, the weld interface area 74 may be moved relative to theinduction coil 22. It should be appreciated that blocks 178, 179, and180 may occur simultaneously. At block 182, feedback from the sensors 38is used to adjust the induction welding process in real time. Forexample, the controller 30 may command different currents to theinduction coil 22, thus adjusting the amount of heating in real time,command a speed between the induction coil 22 and the weld interfacearea 74, etc. At block 184 the second cooling apparatus 100 and/or thesecond induction coil 102 is used to control a rate of cooling of theweld interface area 74. The rate of cooling at the weld interface area74 is controlled by controlling the amount of cooling and heating by thecontroller 30 in real-time based on feedback received from the sensors38 (FIG. 1).

FIG. 19 shows an alternate example of a heat sink 185 according to theprinciples of the present disclosure. The heat sink 185 is configured toabsorb and dissipate heat from the first TPC 12 and/or the second TPC14. The heat sink 185 includes a number of tiles 186 flexibly connectedby a joint 187. The joint 187 is disposed between the tiles 186. Thetiles 186 are substantially similar to the tiles 40 and the joint 187 issubstantially similar to the joint 42 of the heat sink 20 shown in FIG.2. However, the heat sink 185 further includes a number of fluidchannels 188 formed therethrough. The fluid channels 188 extend througheach of the tiles 186 and through each of the joints 187. Sets of fluidchannels 188 between adjacent tiles 186 and the joints 187 are connectedtogether in series to form number of fluid paths 188A through the heatsink 185. The fluid paths 188A are preferably unidirectional andparallel to one another. However, the fluid paths 188A may have otherconfigurations, such as non-parallel or offset. In the example provided,each tile 186 includes three fluid channels 188, however, it should beappreciated that any number of fluid channels 188 may be employed. Thefluid channels 188 are sized to communicate a coolant fluid therethrough, as will be described below. In one example, the fluid channels188 have a diameter of about 0.042 inches. In another example, the fluidchannels 188 have a diameter of about 0.082 inches. In one aspect, amanifold 189 is connected to the heat sink 185. The manifold 189includes a port 190 that communicates via multiple internal channels(not shown) with the fluid channels 188 in order to provide a singleconnection port for the heat sink 185.

FIG. 20 shows a flow chart of a method 200 for creating the heat sink185 using the heat sink fabrication system 50 of FIG. 3. The method 200begins at block 202 where the fluid channels 188 are formed through eachof the tiles 186. In one example, the fluid channels 188 are drilledthrough the tiles 186 using ultra-sonic machining (not shown).

At block 204 a plurality of rods 205, illustrated in FIG. 21, areinserted into the fluid channels 188. The rods 193 may be coated with arelease material to assist in later removing the rods 193. The rods 193are sized to match the diameters of the fluid channels 188. Each of therods 193 passes through multiple tiles 186 having aligned fluid channels188. At block 206 the tiles 186 are arranged into a pattern. Forexample, the tiles 186 are placed onto the backing material 54 betweenthe jig 58. The backing material 54 holds the tiles 186 in place whilethe jig 58 spaces the tiles 186. Thus, the pattern is defined by the jig58. The tiles 186 may be primed by a primer prior to arrangement ontothe backing material 54. The tiles 186 are preferably arranged such thatthe fluid channels 188 are in alignment with one another. It should beappreciated that blocks 204 and 206 may be performed in any orderwithout departing form the scope of the present disclosure.

At block 208 the frame 56 and the jig 58 are removed thus leaving thegaps 44 between the tiles 186. Next, at bock 210, the tiles 40 areflexibly joined together with the flexible adhesive 45. The flexibleadhesive 45 is applied within the gaps 44 between the tiles 186. Therods 205 prevent the flexible adhesive 45 from entering the fluidchannels 188 formed in the tiles 186. In addition, the flexible adhesive45 flows around the rods 205 to form the fluid channels 188 through thejoint 187. The flexible adhesive 45 is then preferably cured over aperiod of time. Once cured, at block 212 the rods 193 are removed fromthe fluid channels 188. The assembled heat sink 185 may be removed fromthe backing material 54.

FIG. 22 shows an enlarged, partial cross-section of the system 10illustrating a lay-up of the first TPC 12, the second TPC 14, and theheat sink 185 on the tooling base 16. The first TPC 12 is disposed ontop of the second TPC 14. The heat sink 185 is disposed on top of thefirst TPC 12 between the induction coil 22 and the first TPC 12. Thefirst roller 28A and the second roller 28B apply a consolidatingpressure on the first TPC 12 through the heat sink 185 to compress thefirst TPC 12 onto the second TPC 14. The fluid paths 188A of the heatsink 185 are connected to a pump 220 that supplies a coolant to the heatsink 185. The pump 220 is configured to pump a coolant, such as water ora high temperature transfer fluid, through the fluid paths 188A of theheat sink 185. An example of a high temperature transfer fluid isDynalene SF by Dynalene. In one example, the pump 220 is connected tothe port 190 (FIG. 19) of the manifold 189.

During induction welding, the controller 30 (FIG. 1) commands a currentthrough the induction coil 22 to generate the magnetic field 25. Themagnetic field 25 heats the carbon fibers within the first TPC 12 andthe second TPC 14. A portion 76 of the first TPC 12 closer to theinduction coil 22 is heated to a greater extent than at the weldinterface area 74. A coolant is pumped through the heat sink 185 by thepump 220. Heat generated in the first TPC 12 is absorbed by the heatsink 185 and dissipated into the coolant in the fluid paths 188A. Thecoolant is pumped out of the heat sink 185, thus dissipating the heat inthe first TPC 12.

When the thermoplastic at the weld interface area 74 is heated above themelting point, or consolidation temperature, of the material, the firstroller 28A and the second roller 28B exert a consolidating pressure onthe first TPC 12 to merge the first TPC 12 with the second TPC 14 at theweld interface area 74, thus creating a uniform fusion bond uponcooling. In one example, the weld interface area 74 is heatedapproximately 20 degrees above the consolidation temperature.

Once heated, the coolant may be pumped back through the heat sink 185 tocontrol a rate of cooling of the weld interface area 74. In one example,the coolant is cycled back through the heat sink 185 at a temperature ofabout 400 degrees Fahrenheit after induction welding to control a rateof cooling of the weld interface area 74. The input temperature and flowrate of the coolant through the heat sink 185, along with the powersupplied to the induction coil 22, may be adjusted to control thecooling rate of the weld interface area 74.

The controller 30 then commands the robotic arm 24 to move in the firstdirection 26A (FIG. 1) along the weld line 26 (FIG. 1) to weld the firstTPC 12 part to the second TPC 14. Alternatively, the weld interface area74 is moved relative to the induction coil 22. Feedback from the sensors38 (FIG. 1) may be used to command different currents to the inductioncoil 22, thus adjusting the amount of heating in real time.

FIG. 23 shows another example of a heat sink 250 according to theprinciples of the present disclosure. The heat sink 250 is similar tothe heat sink 185 shown in FIG. 19, however, the fluid channels 188 aredisposed within the joints 187. Thus, the fluid channels 188 aredisposed between the tiles 186 rather than through the tiles 186. Thetiles 186 are not drilled therethrough and therefore can withstandgreater compressive force than in the heat sink 185. The fluid channels188 are able to withstand the consolidating pressure during inductionwelding without pinching and cutting off the fluid channels 188.

FIG. 24 shows still another example of a heat sink 300 according to theprinciples of the present disclosure. The heat sink 250 is similar tothe heat sink 185 shown in FIG. 19, however, the fluid channels 188 areoval in shape. In addition, only one fluid channel 188 is formed in eachof the tiles 186. The oval shaped fluid channels 188 reduce the pressuredrop and reduce any chance of restrictions within the fluid channel 188,relative to the heat sink 185. Additionally, the oval shaped fluidchannels 188 have increased thermal transfer due to larger surface areasof the fluid channel 188, relative to the heat sink 185. It should beappreciated that other shapes, including square or star, may be employedwithout departing from the scope of the present disclosure.

FIG. 25 shows a top view of a portion of another example of a heat sink400 according to the principles of the present disclosure. The heat sink400 includes a number of tiles 402 connected by a backing 404. The tiles402 are made from an electrically non-conductive and thermallyconductive material and are similar to the tiles 40 (FIG. 2) of the heatsink 20, however, the tiles 402 are hexagonal in shape rather thansquare. However, it should be appreciated that the tiles 402 may haveany number of sides and shapes without departing from the scope of thepresent disclosure. The tiles 402 are fixed in place by the backing 404.

The backing 404 flexibly holds the tiles 402 together and providesflexibility to the heat sink 400, thus allowing the heat sink 400 toconform to a curved surface (not shown). The tiles 402 are arranged in asingle layer in a parquet or geometric pattern. Each of the tiles 402define an air gap 406 therebetween. The air gap 406 is free of material.In one example, the air gap 406 has a width 407 between about 0.005inches to about 0.1 inches and preferably about 0.040 inches. In thiscontext, the term “about” is known to those skilled in the art.Alternatively, the term “about” may be read to mean plus or minus 0.005inches. The air gap 406 allows for increased cooling of the tiles 402using air flow, as will be described below. The backing 404 ispreferably a mesh comprised of interleaved fibers 408, only a few ofwhich are illustrated in FIG. 25. The fibers 408 are non-conductive anddo not melt during induction welding. The fibers 408 may be comprised ofglass or an oxide ceramic and may be embedded in a silicone or othermaterial. In another example, the backing 404 is comprised of afiberglass cloth or mesh infused with Polytetrafluoroethylene (PTFE).

In one example, the heat sink 400 includes a tube 410 disposed along alongitudinal edge 412 of the heat sink 400. In one example, the tube 410is bonded to the backing 404. In another example, the tube 410 iscomprised of PTFE. In addition, or alternatively, the tube 410 may bedisposed in a portion of the heat sink 400 not along the longitudinaledge 412, such as a lateral edge, etc. The tube 410 is connected with asource of pressurized gas 414. The source of pressurized gas 414 mayinclude a fan, pump, or pressurized tank. The source of pressurized gas414 communicates a gas, such as air or cold CO₂, through the tube 410.The tube 410 includes holes 416 disposed therethrough. The holes 416 arealigned with the air gaps 406 between the tiles 402. During inductionwelding, gas is provided by the source of pressurized gas 414 andcommunicated through the tube 410 and through the holes 416. The gasthen passes through the air gaps 406 and absorbs and dissipates heatfrom the tiles 402.

FIG. 26 shows a partial cross-section of the heat sink 400. The tiles402 are adhered to the backing 404 by an adhesive 420. The adhesive 420does not need to be flexible since the backing 404 is flexible. Examplesof suitable adhesives include Silicones, PTFE, Polybenzimidazole (PBI),High-performance polyamides (HPPAs), Polyamide (PIs), Polyamidemides(PAIS), Polyketones, Polysulfone derivatives-a, Flouropolymers,Polyethermides (PEIs), Polybutylene terephthalates (PBTs), Polyphenylenesulfides, Syndiotactic polystyrene, and Polycyclohexanedimethyl-terephthalates (PCTs). Another example of a suitable adhesiveis an epoxy, heat cured, two component system having a liquid resin andpowder hardener. For example, the adhesive may be EPDXYLITE® 5403 orEPDXYLITE® 5302 registered to Elantas PDG, Inc. In another example, theadhesive 420 may be a silicone pressure sensitive adhesive. In anotherexample, the adhesive 420 is comprised of the same type of silicone usedin the joint 42 (FIG. 2) of the heat sink 20. FIG. 27 shows across-section of another variation of the heat sink 450 where the tiles402 are embedded within the adhesive 420. In this example, the air gaps406 are filled with the adhesive 420.

FIGS. 28 and 29 illustrate a partial cross-section of a system 500 forinduction welding the first TPC 12 to the second TPC 14 using the heatsink 400. The system 500 operates in a manner similar to the system 10(FIG. 1) described above. In the example provide, the first TPC 12 andthe second TPC 14 are curved and thus the first TPC 12 defines a curvedcontact surface 502. The first TPC 12 and the second TPC 14 aresupported by a curved tooling base 504. Consolidating pressure duringinduction welding is applied through the curved tooling base 504 by abellows 506. Alternatively, air pressure cylinders or mechanicalactuators, such as springs, straps, or levers, may be used to apply theconsolidating pressure.

The heat sink 400 is disposed on the first TPC 12 between the inductioncoil 22 and the second TPC 14. The backing 404 flexes to allow the tiles402 to contact the curved contact surface 502. Contact between the tiles402 and the curved contact surface 502 maximizes heat transfer. Inanother example (not shown), the backing 404 is infused with PTFE andthe backing 404 is in contact with the curved contact surface 502. ThePTFE allows the backing 404 to act as a release film and prevents theheat sink 400 from sticking to the first TPC 12 during inductionwelding.

The heat sink 400 is held in place by a heat sink holder 508.Alternatively, or in addition, the vacuum bag 70 (FIG. 1) may be used tohold the heat sink 400 in contact with the curved contact surface 502.In one example, shown in FIG. 28, an air gap 510 is formed opposite theweld interface area 74 only when the backing 404 is flexed. In thisexample, air flow is not used to help cool the tiles 402 and the heatsink may only accommodate a curved surface in two dimensions (i.e., xand y coordinates). In another example, shown in FIG. 29, an air gap 512is also formed adjacent the curved contact surface 502 when the backing404 is flexed. In this example, air flow is used through the air gaps510, 512 to help cool the tiles 402. Additionally, the heat sink 400 mayaccommodate a curved surface in three dimensions (i.e., x, y, and zcoordinates). Induction welding is performed in a manner similar to thatdescribed above in reference to FIG. 1.

The systems 10 and 500 described above, the heat sinks 20, 185, 250,300, and 400, as well as the methods 60, 80, 110, 130, 150, and 170 alloperate to control the inductive heating of the first TPC 12 and thesecond TPC 14 to concentrate heating along the weld interface area 74.Thus, temperatures exceeding the consolidation temperature are avoidedin the portion 76 in the first TPC 12 closest the induction coil 22 aswell as the portion 88 in the second TPC 14.

Aspects of the systems 10 and 500, as well as the methods 60, 80, 110,130, 150, and 170, may be employed in the context of an aircraftmanufacturing and service method 1000 as shown in FIG. 30 and anaircraft 1002 as shown in FIG. 31. During pre-production, exemplarymethod 1000 may include specification and design 1004 of the aircraft1002 and material procurement 1006. During production, component andsubassembly manufacturing 1008 and system integration 1010 of theaircraft 1002 takes place. Thereafter, the aircraft 1002 may go throughcertification and delivery 1012 in order to be placed in service 1014.While in service by a customer, the aircraft 1002 is scheduled forroutine maintenance and service 1016 (which may also includemodification, reconfiguration, refurbishment, and so on). Apparatus andmethods embodied herein may be employed during any one or more suitablestages of the production and service described in method 1000 (e.g.,specification and design 1004, material procurement 1006, component andsubassembly manufacturing 1008, system integration 1010, certificationand delivery 1012, service 1014, maintenance and service 1016) and/orany suitable component of aircraft 1002 (e.g., airframe 1018, systems1020, interior 1022, propulsion system 1024, electrical system 1026,hydraulic system 1028, environmental 1030).

Each of the processes of the systems and methods described herein may beperformed or carried out by a system integrator, a third party, and/oran operator (e.g., a customer). For the purposes of this description, asystem integrator may include without limitation any number of aircraftmanufacturers and major-system subcontractors; a third party may includewithout limitation any number of venders, subcontractors, and suppliers;and an operator may be an airline, leasing company, military entity,service organization, and so on.

As shown in FIG. 31, the aircraft 1002 produced by exemplary method 1000may include an airframe 1018 with a plurality of systems 1020 and aninterior 1022. Examples of systems 1020 include one or more of apropulsion system 1024, an electrical system 1026, a hydraulic system1028, and an environmental system 1030. Any number of other systems maybe included. Although an aerospace example is shown, the principles ofthe disclosure may be applied to other industries, such as theautomotive industry.

The system and methods described above may be employed during any one ormore of the stages of the exemplary method 1000. For example, componentsor subassemblies corresponding to component and subassemblymanufacturing 1008 may be fabricated or manufactured in a manner similarto components or subassemblies produced while the aircraft 1002 is inservice. Also, one or more apparatus aspects, method aspects, or acombination thereof may be utilized during the component and subassemblymanufacturing 1008 and system integration 1010, for example, bysubstantially expediting assembly of or reducing the cost of an aircraft1002. Similarly, one or more of apparatus aspects, method aspects, or acombination thereof may be utilized while the aircraft 1002 is inservice, for example and without limitation, to maintenance and service1016. For example, the techniques and systems described herein may beused for material procurement 1006, component and subassemblymanufacturing 208, system integration 1010, service 1014, and/ormaintenance and service 1016, and/or may be used for airframe 1018and/or interior 1022. These techniques and systems may even be utilizedfor systems 1020, including, for example, propulsion system 1024,electrical system 1026, hydraulic 1028, and/or environmental system1030.

The description of the present disclosure is merely exemplary in natureand variations that do not depart from the gist of the presentdisclosure are intended to be within the scope of the presentdisclosure. Such variations are not to be regarded as a departure fromthe spirit and scope of the present disclosure.

The following is claimed:
 1. A heat sink for use in induction welding,the heat sink comprising: a flexible backing; and a number of tilesdisposed on the flexible backing in a single layer, wherein the tilesare electrically non-conductive and thermally conductive.
 2. The heatsink of claim 1, wherein the tiles are spaced apart on the flexiblebacking to form an air gap therebetween.
 3. The heat sink of claim 2,further comprising a tube having a hole, the hole aligned with the airgap and configured to communicate a gas therethrough.
 4. The heat sinkof claim 3, wherein the tube is bonded to the flexible backing.
 5. Theheat sink of claim 4, wherein the tube is disposed along a longitudinaledge of the heat sink.
 6. The heat sink of claim 1, wherein the flexiblebacking is comprised of interwoven fibers.
 7. The heat sink of claim 6,wherein the interwoven fibers include fiberglass or oxide ceramic. 8.The heat sink of claim 1, wherein the flexible backing is infused withpolytetrafluoroethylene.
 9. The heat sink of claim 1, wherein the tilesare spaced apart.
 10. The heat sink of claim 1, wherein the tiles areadhered to the flexible backing by an adhesive.
 11. The heat sink ofclaim 10, wherein the adhesive is disposed between the tiles.
 12. Theheat sink of claim 10, wherein the adhesive is a silicone pressuresensitive adhesive.
 13. The heat sink of claim 10, wherein the adhesiveis selected from the group consisting of Silicones, PTFE,Polybenzimidazole (PBI), High-performance polyamides (HPPAs), Polyamide(PIs), Polyamidemides (PAIS), Polyketones, Polysulfone derivatives-a,Flouropolymers, Polyethermides (PEIs), Polybutylene terephthalates(PBTs), Polyphenylene sulfides, Syndiotactic polystyrene, andPolycyclohexane dimethyl-terephthalates (PCTs).
 14. The heat sink ofclaim 10, and an epoxy, heat cured, two component system having a liquidresin and powder hardener.
 15. A method of induction welding a firstcarbon fiber thermoplastic composite (TPC) to a second carbon fiberthermoplastic composite (TPC), the method comprising: forming a weldinterface area between the first TPC and the second TPC; placing a heatsink onto a surface of the first TPC above the weld interface area;inductively heating the weld interface area; moving a gas through theheat sink; and dissipating heat absorbed by the heat sink bytransferring the heat from the heat sink to the gas.
 16. The method ofclaim 15, further comprising moving the gas through air gaps betweentiles in the heat sink.
 17. The method of claim 15, wherein placing theheat sink onto the surface of the first TPC above the weld interfacearea includes flexing the heat sink onto the surface.
 18. A system forinduction welding a first thermoplastic composite (TPC) to a secondthermoplastic composite (TPC) at a weld interface area, the systemcomprising: a heat sink disposed on the first TPC, the heat sink havinga number of tiles flexibly joined together by a backing and having anair gap disposed between the tiles; and an induction coil configured toinductively weld the first TPC to the second TPC at the weld interfacearea, the induction coil disposed adjacent the heat sink.
 19. The systemof claim 18, further comprising a source of pressurized gas connected tothe heat sink for moving a gas through the air gap of the heat sink. 20.The system of claim 18, further comprising a heat sink holder disposedon the heat sink for applying a consolidating pressure onto the heatsink during induction welding.